The invention relates to a noncontacting displacement sensor with a measuring coil to which alternating current can be applied, the measuring coil having at least two voltage taps, with an electrically and/or magnetically conductive measuring object, and with an evaluation circuit for evaluating and, if need be, determining an output voltage corresponding to the position of the measuring object with respect to the voltage taps.
A noncontacting displacement sensor of the kind under discussion is also disclosed in WO 94 03778 and corresponding U.S. Pat. No. 5,629,619. The measuring coil of the known sensor has plurality of voltage taps that are arranged at defined intervals, and it is enclosed in a casing. The measuring object is a ring that surrounds the casing in spaced relationship and is displaceable along the casing wall. With the use of the known displacement sensor it is possible to determine the position of the ring with respect to the voltage taps arranged on the measuring coil. The presence of the ring between two voltage taps is effective on the impedance of the measuring coil segment that extends between these voltage taps and on all such "partial" impedances of segments of the measuring coil that follow in one direction. This means, that depending on the location of the measuring coil in which the ring is positioned, a varying quantity of partial impedances are influenced. With the known displacement sensor, voltages that can be tapped on successive segments of the measuring coil are added. In each instance, subtotals are formed which differ in the increasing number of considered voltage values. These subtotals are again added to an output voltage that may then be clearly related to the position of the ring.
The measuring object of the known displacement sensor is located outside of the coil casing. As a result, the measuring object is relatively exposed and unprotected. Furthermore, the known displacement sensor requires relatively much space, so as to ensure a mobility of the measuring object on the outer side of the coil casing.
It is therefore the object of the invention to describe a noncontacting displacement sensor of the kind under discussion that is of an as compact design as possible and requires for itself only relatively little space.